Electromagnetic self-priming pump

ABSTRACT

An electromagnetically driven, self-priming, liquid pump comprising a pump cylinder having a liquid passage with an inlet and an outlet, a pair of magnetizable pumping pistons which are received in the passage for movement toward and away from each other to pump liquid from the inlet to the outlet, an electromagnetic coil for magnetizing the pistons in such a manner as to cause them to be attracted to each other when the coil is energized, and a yieldable member for moving the pistons apart.

United States Patent 1191 1111 3,841,798

Rehfeld Oct. 15, 1974 1 ELECTROMAGNETIC SELF-PRIMING 3,629,674 12/1971 Brown 417 415 PUMP FOREIGN PATENTS OR APPLICATIONS Inventor! Fred Rehield, Saginaw, Mich- 823,109 11/1959 Great Britain 417/416 [73] Assignee: ODell Manufacturing Inc., Saginaw,

Mich. Primary Examiner-C. .1. Husar Fned: Mar. 1973 Attorney, Agent, or F1rm-Learman & McCulloch An electromagnetically driven, self-priming, liquid [52] US. Cl 417/419, 417/415, 310/34 pump comprising a pump cylinder having a liquid [51] Int. Cl. F041) 35/04 Sage with an inlet and an outlet, a pair of magnetizable [58] Field of Search 417/415, 416, 419; 310/34, pumping pistons which are received in the passage for 310/24 movement toward and away from each other to pump liquid from the inlet to the outlet, an electromagnetic [56] References cued coil for magnetizing the pistons in such a manner as to UNITED S S PATENTS cause them to be attracted'to each other when the coil 2,468,343 4 1949 Parker 310 34 is energized, n a y lda l m mber for moving the 2,495,598 1/1950 Parker.... 310/34 pistons apart. 3,486,456 12/1969 Hager et al. 417/416 3,542,495 11/1970 Barthalon 417/416 35 Claims, 6 Drawing Figures 1 ELECTROMAGNETIC SELF-PRIMING PUMP BACKGROUND OF THE INVENTION This invention relates to an electromagnetically driven, self-priming, fluid pump, including a pair of reciprocating pumping pistons which are magnetized to move together when subjected to a magnetic field and are moved apart by yieldable means storing energy in response to the pistons being moved together.

It is an object of the present invention to provide an electromagnetically driven, self-priming pump having a pair of magnetizable, liquid pumping pistons which are moved together in response to being subjected to a magnetizing field.

It is another object of the present invention to pro vide an electromagnetically driven, fluid pump having a pair of axially aligned pumping pistons which are alternately magnetized in opposite directions and in such a manner so as to be attracted toward each other each time they are magnetized.

Yet another object of the present invention is to provide a self-priming, electromagnetically driven, fluid.

pump having an axial pumping cylinder with an inlet and an outlet, a pair of axially aligned pumping pistons movable together and apart in the cylinder for moving fluid downstream from the inlet to the outlet, each of the pistons having a magnetizable portion and a perimetrical sealing flange portion which seals to the cylinder wall when the piston is moved downstream, but radially collapses to permit fluid to flow thereby when the piston is moved upstream.

A further objectof the present invention is to provide a self-priming, electromagnetically driven pump having a pair of aligned, pumping pistons with magnetizable portions, an electromagnetic, flux field creating coil energized by an electrical source of alternating current to alternately magnetize the magnetizable portions in opposite directions on opposite half cycles of the alternating current, and a yieldable member responsive to movement of said portions in one direction to move them in an opposite direction sothat the pumping frequency is twice the alternating current frequency.

Other objects and. advantages of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.

SUMMARY OF THE INVENTION An electromganetically driven, liquid pump comprising: a pump cylinder defining a liquid passage having a liquid inlet and a liquid outlet; a pair of magnetic field responsive, liquid pumping members which are movable in the passage between spread positions and closed positions for pumping liquid from the inlet to the outlet, an electromagnetic coil for establishing magnetic flux of alternately increasing and decreasing density within the passage to' move the liquid pumping members'to one of the closed and spread positions when the flux density is increasing and permit movement of the piston members to the other of the closed and spread positions when the flux density is decreasing; and an energy storing yieldable member responsive to movement of the liquid pumping members to the one of the closed and spread positions for moving the piston members to the other of the closed and spread positions when the magnetic flux density is decreasing.

The present invention may more readily be understood by reference to the accompanying drawings, in which:

FIG. 1 is a vertical, sectional view of an electromagnetically driven, liquid pump constructed according to the present invention, taken along the line l-1 of FIG. 2;

FIG. 2 is a sectional top plan view of the pump taken along the line 22 of FIG. 1; and

FIGS. 3 through 6 are sectional side views illustrating various positions of a pair of liquid pumping pistons throughout a pumping cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENT A self-priming, electromagnetic pump constructed according to the present invention is generally designated l0 and includes a ring-shaped, generally rectangular magnetic core, generally designated 12, having a pair of top and bottom legs 14 and 16 and end legs 18 and 20 forming a continuous, closed path for magnetic flux. The iron core 12 may suitably comprise a plurality of stacked, laminations of magnetizable material, to minimize hysteresis losses.

A pair of apertures 22 are provided in the upper and lower magnetic core legs 14 and 16 to receive a vertical pump cylinder 24 defining a liquid passage 26 having a lower, inlet end 28 immersed in water, or other fluid to be pumped, and an upper discharge end 30. The cyl- 'inder 24 is fabricated from non-magnetic material such as glass.

Disposed in the liquid passage 26 is a pair of upper and lower pumping pistons generally designated 32 and 34. The pumping piston 32 includes a cylindrical, magnetizable core 36 of, for example, iron bonded to a relatively soft liner of resilient material 38 which terminates in an axially downstream flange 40, normally flaring radially outwardly into sealing engagement with the cylinder wall 24, but being collapsible radially inwardly to the position shown in FIG. 5, permitting fluid to pass thereby. Water W- is forced axially past the resilient liner 38, in the, direction of the arrow b (FIG. 5) in a manner to be later described. When the sealing flange 40 engages the cylinder wall 24, the piston 32 moves water axially downstream in the direction of the arrow v j (FIGS. 1 and 6) to the outlet 30.

The resilient liner 38 includes an integral end wall 48 having an additional flange portion 46 at the opposite, or upstream, end of the piston 32 which extends axially downstream and normally flares radially outwardly into engagement with the cylinder wall 24, but is collapsible radially inwardly when the piston 32 moves upstream to the position illustrated in FIG. 1 so that water W can move in the direction of the arrow b (FIG. 5) between the flange 46 and the wall 24. The flange 46, in addition to providing a pumping action as it moves downstream toward the outlet 30, also functions to center the piston 32 in the cylinder 24. The liner end wall 48 functions as an energy storing, yieldable cap which covers the lower end wall of the upper piston core 36 and it will be noted that it is provided with a protuberance 48a for a purpose to be presently described.

The lower pumping piston 34 includes a magnetizable, elongate, central core 50 bonded to a like liner of resilient material 52. The liner 52 includes an integral terial which covers the upper or downstream end wall of the piston core 50 and has a protuberance or node 54a for engaging the resilient protuberance or node 48a on the upper piston as the pistons 32 and 34 are moved together in a manner to be later described'As the pistons are drawn together, the resilient end portions 48 and 54 are compressed to store energy and, after a predetermined deformation or compression, operate to move the pistons 32 and 34 apart as will also be later described. The upper end resilient portion 54 includes an integral, axially downstream flange 56, identical to the upper piston flange 40, normally flaring radially outwardly into sealing engagement with the cylinder wall, but deflectable or collapsible radially inwardly to permit water-W to pass between theflange 56 and cylinder wall 24. The resilient liner 52, at the axially lower end of the piston 34, includes a centering flange 58 extending axially and normally flaring radially outwardly into sealing engagement with the cylinder wall 24 to pump water W upwardly in the direction of the arrowc (FIG. 1). The flange 58 is similarly deflectable inwardly to perm-it water W to pass thereby. A perforated resilient support disc 60, having apertures 61, permitting the upward flow of water W, is disposed in the lower end of the pumping passage 26 to prevent the lower pumping piston 34 from dropping through the inlet end 28 of the cylinder 24 when the pump is not in operation. The resilient material 48 and 54 may suit.- ably comprise natural, vulcanized rubber or silicone rubber. The material can be selected to provide a spring rate providing the optimum pumping force. Silicone rubber of the type sold underthe trademark RTV-l08 by General Electric Company, Schenectady, New York, has been found suitable for this purpose.

An electrically energizable, electromagnetic, toroidal coil 62 surrounds the nonmagnetic pumping cylinder 24 and the pistons 32 and 34 whichtogether effectively netic flux field in the pump passage 26. On the positive half cycle of the current from'source 66, the flux generated by the coil-62 will follow thepath designated by the arrow d in the direction designated by the arrows 2. On the opposite or negative half cycle of the current from source 66, the flux generated by the coil 62 will follow the reverse path illustrated in chain lines at 0, in the opposite direction represented by the arrow p.

' THE OPERATION In operation, the pump inlet end 28 is immersed in the water W and'the coil leads 64 are connected to the A.C. source 66. It will'be assumed that the pistons 32 and 34 are initially in the spread positions illustrated in chain lines in FIG. 1 and that the winding 62 is initially energized by a positive half cycle of current alternating so that the flux'emanating from the coil 62 will follow the path d (FIG. 3) to magnetize the piston cores 36 and such that the lower end of the core 36 has a south polarity and the upper end of'the core 50 is of opposite, or north, polarity.'The adjacent ends of the cores will thus be attracted to eachother and the pistons 32 and 34 will move together to'the positions illustrated in FIG. 3. When the pistons 32 and 34 are brought together, the resilient end portions 48 and 54 engage and are compressed (FIG. 5) to store energy.

As the energizing current on the first half cycle decreases and the resultant flux decreases after some lag, the stored energy in the compressed, resilient material nodes 48 and 54 overcomes the magnetic forces attracting the magnetic cores 36 and 50 together, pushing the pistons 32 and 34 to the spread positions illustrated in FIG. 4. When this occurs, a partial vacuum is created in the collapsible chamber (FIG. 4) between the pistons 32 and 34. Since the pressure on the axially downstream sides of the lower piston flanges 56 and 58 is less than the pressure on the upstream side of the lower piston flanges, the water W will move upwardly through the openings 61 in the support 60, axially past the flanges 56 and 58 in the direction of the arrow g (FIG. 4) into the chamber 70.

The electromagnetic coil 62 is then energized by the alternate half cycle of the alternating current to provide flux in the path p to oppositely magnetize the cores 36 and 50 so that the lower end of the upper core 36 is'now of a north polarity and the upper end of the lower core 50 is now of opposite, or south, polarity so that the adjacent ends of the cores 36 and 50are again attracted and the pistons 32 and 34 are again brought together to the positions illustrated in FIG. 5 to diminish the chamber 70 and force the fluid in the chamber 70 upwardly past the upper piston flanges 46 and 40 in the direction of the arrows b and h (FIG. 5). The increasing pressure in the chamber 70 on the downstream side of the upper piston flanges 46 and 40 is greater than the pressure on the upstream side of the flanges 46 and 40 so that the fluid is forced thereby. The pressure exerted by the fluid in the chamber 70 on the downstream side of the lower piston flanges 46 and 58, in the direction of the arrow i (FIG. 5) tends to.

move the flanges 56 and 58 radially outwardly into sealing engagement with the cylinder 24 to prevent water W in the chamber 70 from flowing toward the inlet 28. The resilient members 48 and 50 are again compressed and the'energy stored in the resilient energy storing, resilient members 48 and 50 forces the pistons to the spread positions illustrated in FIG. 6, so that water W is again drawn upwardly past the lower piston flanges 56 and 58, in the direction of the arrow g, and concurrently the fluid which has been expelled past the upper piston upper flange 40 is moved axially outwardly in the direction of the arrow j (FIG. 6) to the outlet 30. The pressure exerted by the expelled fluid, on the downstream side of the flanges 40 and 46 in the direction of the arrow k, forces the flanges 40 and 46 radially-outwardly into sealing engagement with the wall 24 to prevent movement of the expelled fluid toward the inlet. The pistons 32 and 34 are thus moved toward and away from each other at times a minute so that the pumping frequency is twice the alternating current frequency.

I It is to be understood that the drawingsand tive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that .various changes may be made in various ele-' ments to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is: l 1. An electromagnetically driven, liquid pump comprising:

descriphousing means having an axial liquid passage with an inlet and an outlet; pumping mechanism comprising a pair of axially aligned, magnetizable, liquid pumping means received in said passage, at least one of said pumping means being mounted for axial movement between a removed position in which said pumping means are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a position in which said pumping means are less spread to pump liquid from said chamber to said outlet;

magnetic field producing means for magnetizing said pair of liquid pumping means-such that the axially adjacent ends thereof are of opposite magnetic polarity and attracted toward each other to move at least said one pumping means toward the other;

said liquid pumping means comprising elements of magnetizable material disposed in axial prolongation of'each other in said passage;

said magnetic field producing means comprising electromagnetic coil means including means for establishing an alternating flux which alternately magnetizes said elements in opposite directions to alternately reverse the polarity of the elements so that the adjacent ends of said elements are of opposite polarity and attracted to each other each time the elements are magnetized; and

yieldable means reactable to store energy in response to movement of said one liquid pumping means toward the other to force said one liquid pumping means to said removed position.

2. The pump set forth in. claim 1 wherein the piston means each include radially collapsible and expandable seal means, engageable with said passage'means in the expanded condition to prevent the flow of fluid toward said inlet, and spaced from said chamber means in the collapsed condition to permit the flow of fluid downstream from said inlet to said outlet.

3. An electromagnetically driven, liquid pump comprising:

housing means having an axial liquid passage with an inlet and an outlet;

pumping mechanism comprising a pair of axially aligned, magnetizable, liquid pumping means received in said passage, at least one of said pumping means being mounted for axial movement berween a removed position in which said pumping means are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a position in which said pumping means 'are less spread to pump liquid from said chamber to said outlet;

said pumping mechanism comprising a pair of piston means movable between axially spread positions to provide said chamber and less spreadpositions; one of said piston means including means permitting the flow of fluid from said inlet to said chamber when said piston means are moving to said spread positions, butpreventing reverse flow when said piston means are moving together;

magnetic field producing means for magnetizing said pair of liquid pumping means such that the axially adjacentends thereof are of opposite magnetic polarity and attracted toward each other to move at least said one pump-means toward the other; and

yieldable means reactable to store energy in response to movement of said one liquid pumping means toward the other to force said one liquid pumping means to said removed position.

4. The pump set forth in claim 3 wherein said seal means flares radially outwardly in an axially downstream direction.

5. An electromagnetically driven, liquid pump comprising:

a pump housing having a liquid passage with an inlet and an outlet, said passage being non-magnetizable;

pump mechanism comprising a pair of magnetic field responsive, liquid pumping means in said passage, at least one of said pumping means being movable toward and away from the other between a removed position in which said pumping means are spread and a position in which said pumping means are less spread;

said liquid pumping means comprising a pair of piston means movable toward and away from each other in said passage between spread and closed positions; said piston means providing a variable volume chamber, having a partial vacuum, between said piston means in said spread position for receiving liquid from said inlet;

electromagnetic coil means for establishing a magnetic flux field of alternately increasing and decreasing magnetic flux density within said passage to move said one pumping means to one of said positions when said flux density is increasing; and

energy storing yieldable means, responsive to movement of said one pumping means to said one position, for moving the other of said pumping means to said other of said positions when said magnetic flux density is decreased.

6. The pump of claim 5 wherein said piston means move to said closed positions in response to said increasing field and said yieldable means moves said piston means to said spread positions.

7. The pump of claim 5 wherein said piston means each comprises an element of magnetizable material disposed in axial prolongation of the other element, said electromagnetic coil means includes;

means for establishing a first flux field to magnetize each element so that adjacent ends of said elements have an opposite polarity and are attracted together;

means for disestablishing said first flux field and establishing an opposite flux field to magnetize each element in an opposite direction so that the polarities of the adjacent ends of said elements is reversed and the adjacent element ends are again attracted to each other;

said yieldable means being operative to move said piston means to said spread positions when said first flux field is disestablished.

8. The pump set forth in claim 5 wherein said energy storing yieldable means reacts between said piston means to move said piston means to a spread position.

9. The pump set forth in claim 5 wherein said means for energizing said coil means comprises a source of alternating current.

10. The pump set forth in claim 5 wherein said energizing means comprises means for reversing the current through said coil means to reverse the direction of the magnetic flux. 11. An electromagnetic pump comprising:

a pump housing having a pumping passage therein with an inlet and an outlet at opposite ends thereof;

a pair of magnetic field responsive, liquid pumping piston means disposed in said passage for axial movement toward and away from each other between axially spread positions, and adjacent positions, to pump liquid downstream from said inlet to said outlet; and

means, including magnetic field producing apparatus, for moving said piston means between said spread and said adjacent positions;

each piston means including a body of magnetizable material,

resilient seal means surrounding said body and having a perimetrical flange portion, extending radially outwardly, sealingly engageable with the walls of said passage when said piston means is moving downsteam to prevent fluid from returning upstream, but collapsible radially inwardly when said piston means is moving upstream to permit fluid to pass.

12. The pump of claim 11 wherein said flange portion is at the downstream end of each piston means and flares radially outwardly in an axially downstream direction.

13. The pump of claim 12 wherein said seal means includes an additional radially extending piston means centering flange portion at the other end of each piston means. i

14. The pump of claim 12 wherein means is provided at the upstream end of each piston means for maintaining the axial alignment of said piston means in said passage.

IS. The pump of claim 11' wherein yieldable energy storing means is disposed between said bodies to move the bodies to said spread positions after they are moved to said adjacent positions.

l6.'The pump of claim 11 including support means in said passage axially outwardly of one of said piston means to limit the axial movement of said one piston means in a direction away from the other piston means.

means for cyclically moving said piston means toward and away from each other at twice the frequency of said alternating current including:

an electromagnetic coil, connected with said source and means providing an alternating flux field in said passage which alternately magnetizes said magnetizable portions in opposite directions with opposite half cycles of said flux field to cause said magnetizable portions to be attracted and moved toward each other on each half cycle of the flux; and

means responsive to said magnetizable piston means moving together on each flux half cycle for spreading said piston means to said spread positions.

18. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having an axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced members, at least one of said members comprising a magnetizable liquid pumping structure, having a to-and-fro stroke, mounted for axial pumping movement in said passage between a removed position in which said members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position in which .said members are more closely spaced; said pumping mechanism including seal means for admitting liquid to said chamber while otherwise restricting backflow and permitting liquid to be pumped in a downstream direction fromsaid chamber to said outlet while otherwise restricting backflow, and including collapsible resilient seal means projecting generally laterally outwardly from the perimeter of at least said'one member to engage the housing portion defining said liquid passage; and an assembly for cyclically moving at least said one member relative to the other member, including magnetic field creating means connected with said source to cause at least said one member to be moved.

19. The combination defined in claim 18 in which said magnetizable member comprises a magnetizable core with a sheath having said seal means in the form of a flange which flares axially in a downstream direction.

20. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having a non-magnetizable, magnetic flux permeable, axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced magnetizable members having magnetically confronting portions, atleast one of said members comprising a liquid pumping structure, having a to-andfro stroke, mounted for axial pumping movement in said passage between a removed position in which said magnetizing members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position in which said magnetizing members are magnetically interreactive; and an assembly for cyclically moving at least said one member relative to the other member, said assembly including magnetic field creating means connected with said source, and continuously providing an alternating flux field of predetermined frequency, with flux half cycles of opposite polarity, which alternately magnetizes the confronting portions of said magnetizable .members during opposite half cycles of said flux field to cause said members to magnetically interreact and at least said one member to be moved in the same direction during each half cycle of the flux field.

21. The combination as set forth in claim 20 wherein said magnetic field creating means is connected with a source of alternating current.

22. The combination as set forth in claim 20 wherein said magnetic field creating means comprises a coil for magnetizing the confronting portions of said members so that they are of opposite magnetic polarity and attract one another.

23. The pump as set forth in claim wherein a bias ing device is provided for returning said one magnetizable member to original position at the end of each flux half cycle, and comprises yieldable means reactable to store energy in response to movement of said one member toward the other.

24. The pump as set forth in claim 20 wherein said magnetizable members are disposed in said passage in axial alignment and said magnetic field creating means includes a coil and core which alternately oppositely magnetize the members to alternately reverse the polarity of the confronting portions of the members.

25. The pump as set forth in claim 20 wherein said members include valve structure permitting the flow of fluid from the inlet to the chamber when said one member is moving to dispose the members in spread position but preventing reverse flow when the member is moving to dispose the members in less spread position.

26. The pump as set forth in claim wherein the valve structure comprises radially collapsible and expandable perimetral seals provided on said members which are engageable with the passage in an expanded condition to prevent the flow of fluid toward the outlet, and spaced from the passage in the collapsed condition to permit the flow of fluid toward the outlet.

27. The pump as set forth in claim 26 wherein the seals project radially outwardly and normally flare in an axially downstream direction.

28. The pump as set forth in claim 27 wherein said seals comprise flanges provided on resilient sleeves for the members which do not magnetically shield the members.

29. The pump as set forth in claim 28 wherein flanges are provided at both the downstream and upstream ends of each member to provide axial alignment.

30. The pump as set forth in claim 25 wherein va deformable resilient rubber element is provided between said members to restore the spread disposition of members.

31. The pump as set forth in claim 20 wherein said magnetizable members comprise movable pistons in said passage and structure provided for returning said one magnetizable member to original position returns both members to original position and is disposed between and reactable with both pistons.

32. The pump as set forth in claim 25 wherein yieldable energy storing means to return the members to spread disposition comprises a resilient protrusion on at least one of said members.

33. The pump as set forth in claim 32 wherein said yieldable energy storing means comprises a central protrusion on each of said members which are engaged and deformed when the members move together, and resiliently move the members to spread positions at the end of each flux half cycle.

34. The pump as set forth in claim 20 wherein a perforated stop device in said passage limits the axial movement of at least one of the pistons in a direction away from the other.

35. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having an axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced magnetizable members, at least one of said members comprising a liquid pumping structure, having a to-and-fro stroke, mounted for axial pumping movement in said passage between a removed position in which said magnetizable members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position; an assembly for cyclically moving at least said one member relative to the other member; said assembly including magnetic field creating means connected with said source, and continuously providing an alternating flux field of predetermined frequency, with flux half cycles of opposite polarity, which alternately oppositely polarize said magnetizable members during opposite half cycles of said flux field to cause at least said one member to be moved in the same direction during each half cycle of the flux field; and resilient means for returning said one member in the opposite direction during each half cycle of the flux field. 

2. The pump set forth in claim 1 wherein the piston means each include radially collapsible and expandable seal means, engageable with said passage means in the expanded condition to prevent the flow of fluid toward said inlet, and spaced from said chamber means in the collapsed condition to permit the flow of fluid downstream from said inlet to said outlet.
 3. An electromagnetically driven, liquid pump comprising: housing means having an axial liquid passage with an inlet and an outlet; pumping mechanism comprising a pair of axially aligned, magnetizable, liquid pumping means received in said passage, at least one of said pumping means being mounted for axial movement berween a removed position in which said pumping means are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a position in which said pumping means are less spread to pump liquid from said chamber to said outlet; said pumping mechanism comprising a pair of piston means movable between axially spread positions to provide said chamber and less spread positions; one of said piston means including means permitting the flow of fluid from said inlet to said chamber when said piston means are moving to said spread positions, but preventing reverse flow when said piston means are moving together; magnetic field producing means for magnetizing said pair of liquid pumping means such that the axially adjacent ends thereof are of opposite magnetic polarity and attracted toward each other to move at least said one pump-means toward the other; and yieldable means reactable to store energy in response to movement of said one liquid pumping means toward the other to force said one liquid pumping means to said removed position.
 4. The pump set forth in claim 3 wherein said seal means flares radially outwardly in an axially downstream direction.
 5. An electromagnetically driven, liquid pump comprising: a pump housing having a liquid passage with an inlet and an outlet, said passage being non-magnetizable; pump mechanism comprising a pair of magnetic field responsive, liquid pumping means in said passage, at least one of said pumping means being movable toward and away from the other between a removed position in which said pumping means are spread and a position in which said pumping means are less spread; said liquid pumping means comprising a pair of piston means movable toward and away from each other in said passage between spread and closed positions; said piston means providing a variable volume chamber, having a partial vacuum, between said piston means in said spread position for receiving liquid from said inlet; electromagnetic coil means for establishing a magnetic flux field of alternately increasing and decreasing magnetic flux density within said passage to move said one pumping means to one of said positions when said flux density is increasing; and energy storing yieldable means, responsive to movement of said one pumping means to said one position, for moving the other of said pumping means to said other of said positions when said magnetic flux density is decreased.
 6. The pump of claim 5 wherein said piston means move to said closed positions in response to said increasing field and said yieldable means moves said piston means to said spread positions.
 7. The pump of claim 5 wherein said piston means each comprises an element of magnetizable material disposed in axial prolongation of the other element, said electromagnetic coil means includes; means for establishing a first flux field to magnetize each element so that adjacent ends of said elements have an opposite polarity and are attracted together; means for disestablishing said first flux field and establishing an opposite flux field to magnetize each element in an opposite direction so that the polarities of the adjacent ends of said elements is reversed and the adjacent element ends are again attracted to each other; said yieldable means being operative to move said piston means to said spread positions when said first flux field is disestablished.
 8. The pump set forth in claim 5 wherein said energy storing yieldable means reacts between said piston means to move said piston means to a spread position.
 9. The pump set forth in claim 5 wherein said means for energizing said coil means comprises a source of alternating current.
 10. The pump set forth in claim 5 wherein said energizing means comprises means for reversing the current through said coil means to reverse the direction of the magnetic flux.
 11. An electromagnetic pump comprising: a pump housing having a pumping passage therein with an inlet and an outlet at opposite ends thereof; a pair of magnetic field responsive, liquid pumping piston means disposed in said passage for axial movement toward and away from each other between axially spread positions, and adjacent positions, to pump liquid downstream from said inlet to said outlet; and means, including magnetic field producing apparatus, for moving said piston means between said spread and said adjacent positions; each piston means including a body of magnetizable material, resilient seal means surrounding said body and having a perimetrical flange portion, extending radially outwardly, sealingly engageable with the walls of said passage when said piston means is moving downsteam to prevent fluid from returning upstream, but collapsible radially inwardly when said piston means is moving upstream to permit fluid to pass.
 12. The pump of claim 11 wherein said flange portion is at the downstream end of each piston means and flares radially outwardly in an axially downstream direction.
 13. The pump of claim 12 wherein said seal means includes an additional radially extending piston means centering flange portion at the other end of each piston means.
 14. The pump of claim 12 wherein means is provided at the upstream end of each piston means for maintaining the axial alignment of said piston means in said passage.
 15. The pump of claim 11 wherein yieldable energy storing means is disposed between said bodies to move the bodies to said spread positions after they are moved to said adjacent positions.
 16. The pump of claim 11 including support means in said passage axially outwardly of one of said piston means to limit the axial movement of said one piston means in a direction away from the other piston means.
 17. A pump comprising: cylinder means having a liquid receiving pump passage with an inlet and an outlet; a pair of magnetizable fluid pumping piston means, received in said passage for movement toward and away from each other between adjacent positions and spread positions to pump liquid from said inlet to said outlet; a source of alternating current, having a predetermined frequency; means for cyclically moving said piston means toward and away from each other at twice the frequency of said alternating current including: an electromagnetic coil, connected with said source and means providing an alternating flux field in said passage which alternately magnetizes said magnetizable portions in opposite directions with opposite half cycles of said flux field to cause said magnetizable portions to be attracted and moved toward each other on each half cycle of the flux; and means responsive to said magnetizable piston means moving together on each flux half cycle for spreading said piston means to said spread positions.
 18. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having an axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced members, at least one of said members comprising a magnetizable liquid pumping structure, having a to-and-fro stroke, mounted for axial pumping movement in said passage between a removed position in which said members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position in which said members are more closely spaced; said pumping mechanism including seal means for admitting liquid to said chamber while otherwise restricting backflow and permitting liquid to be pumped in a downstream direction from said chamber to said outlet while otherwise restricting backflow, and including collapsible resilient seal means projecting generally laterally outwardly from the perimeter of at least said one member to engage the housing portion defining said liquid passage; and an assembly for cyclically moving at least said one member relative to the other member, including magnetic field creating means connected with said source to cause at least said one member to be moved.
 19. The combination defined in claim 18 in which said magnetizable member comprises a magnetizable core with a sheath having said seal means in the form of a flange which flares axially in a downstream direction.
 20. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having a non-magnetizable, magnetic flux permeable, axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced magnetizable members having magnetically confronting portions, at least one of said members comprising a liquid pumping structure, having a to-and-fro stroke, mounted for axial pumping movement in said passage between a removed position in which said magnetizing members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position in which said magnetizing members are magnetically interreactive; and an assembly for cyclically moving at least said one member relative to the other member, said assembly including magnetic field creating means connected with said source, and continuously providing an alternating flux field of predetermined frequency, with flux half cycles of opposite polarity, which alternately magnetizes the confronting portions of said magnetizable members during opposite half cycles of said flux field to cause said members to magnetically interreact and at least said one member to be moved in the same direction during each half cycle of the flux field.
 21. The combination as set forth in claim 20 wherein said magnetic field creating means is connected with a source of alternating current.
 22. The combination as set forth in claim 20 wherein said magnetic field creating means comprises a coil for magnetizing the confronting portions of said members so that they are of opposite magnetic polarity and attract one another.
 23. The pump as set forth in claim 20 wherein a biasing device is provided for returning said one magnetizable member to original position at the end of each flux half cycle, and comprises yieldable means reactable to store energy in response to movement of said one member toward the other.
 24. The pump as set forth in claim 20 wherein said magnetizable members are disposed in said passage in axial alignment and said magnetic field creating means includes a coil and core which alternately oppositely magnetize the members to alternately reverse the polarity of the confronting portions of the members.
 25. The pump as set forth in claim 20 wherein said members include valve structure permitting the flow of fluid from the inlet to the chamber when said one member is moving to dispose the members in spread position but preventing reverse flow when the member is moving to dispose the members in less spread position.
 26. The pump as set forth in claim 25 wherein the valve structure comprises radially collapsible and expandable perimetral seals provided on said members which are engageable with the passage in an expanded condition to prevent the flow of fluid toward the outlet, and spaced From the passage in the collapsed condition to permit the flow of fluid toward the outlet.
 27. The pump as set forth in claim 26 wherein the seals project radially outwardly and normally flare in an axially downstream direction.
 28. The pump as set forth in claim 27 wherein said seals comprise flanges provided on resilient sleeves for the members which do not magnetically shield the members.
 29. The pump as set forth in claim 28 wherein flanges are provided at both the downstream and upstream ends of each member to provide axial alignment.
 30. The pump as set forth in claim 25 wherein a deformable resilient rubber element is provided between said members to restore the spread disposition of members.
 31. The pump as set forth in claim 20 wherein said magnetizable members comprise movable pistons in said passage and structure provided for returning said one magnetizable member to original position returns both members to original position and is disposed between and reactable with both pistons.
 32. The pump as set forth in claim 25 wherein yieldable energy storing means to return the members to spread disposition comprises a resilient protrusion on at least one of said members.
 33. The pump as set forth in claim 32 wherein said yieldable energy storing means comprises a central protrusion on each of said members which are engaged and deformed when the members move together, and resiliently move the members to spread positions at the end of each flux half cycle.
 34. The pump as set forth in claim 20 wherein a perforated stop device in said passage limits the axial movement of at least one of the pistons in a direction away from the other.
 35. A liquid pump adapted to be operated by a source of electric current comprising: a pump housing having an axially extending liquid passage with an inlet and an outlet; a liquid pumping mechanism including axially spaced magnetizable members, at least one of said members comprising a liquid pumping structure, having a to-and-fro stroke, mounted for axial pumping movement in said passage between a removed position in which said magnetizable members are axially spread to provide a liquid receiving chamber therebetween for receiving liquid from said inlet, and a less spread position; an assembly for cyclically moving at least said one member relative to the other member; said assembly including magnetic field creating means connected with said source, and continuously providing an alternating flux field of predetermined frequency, with flux half cycles of opposite polarity, which alternately oppositely polarize said magnetizable members during opposite half cycles of said flux field to cause at least said one member to be moved in the same direction during each half cycle of the flux field; and resilient means for returning said one member in the opposite direction during each half cycle of the flux field. 